This double ended brush pen has two tips allowing you to blend or change color as you go. One end has a medium sized soft tip brush head that releases black water-soluble dye based ink and the other end has a smaller soft brush tip that releases grey water-soluble dye based ink. The soft brush tips are more flexible than the normal ones making it easier to create thick or thin strokes.
Fude pens are a type of brush pen used traditionally for Japanese calligraphy but are a great tool for many artists. The brush pens either have brush tips made with brush fibres or fibre/foam tips that mimic a brush shape. They are roughly the size of normal marker pens making them convenient to travel with and easy to pack away.